Voice-operated repeater system



March 2 1926. 1,574,781

H. A. BARTON VOICE OPERATED REPEATIER SYSTEM Filed Oct. 23, 1923 2 Sheets-Sheet vIL l z' lag/ flwal I f( n a ,42 uu l 1 l Il [LI/etectar l 51 46 l A'A'A'A'A'A IN VEN TOR BY ZM ATTQNEY March 2 1926.

lH. A. BARTON VOICE OPERATED REPEATER lSYSTEM Filed Oct. 25, 1923 2 Sheets-Sheet 2 Zrm/.w/ //f/,/f/M/ [Y /lfra/f//e/m/t 2,7) (j) E y E @y ff L4@ order that the controlling current may be Patented Mar. 21, i926.

U Nrrr stares PATENT ortica.:

HENRY A. IiBARTON, 0.1i' PRINCETON, NEW JERSEY, ASSIGNOR T0 AMERICAN TELE- 'PHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

vorcn-ornnn'rnn REPEATER SYSTEM.

Application led October 23, 1923. Serial No. 670,313.

Toall whom t may concern: v

Be it known that I, HENRY A. BARTON, residing at Princeton, in the county of Mercer and State of New Jersey, have invented certain Improvements in Voice-Operated Repeater Systems, of which the following is a specification.

This invention relates to repeater systems and more particularly to a system in which one-way repeaters may be used on two-wire circuits.

Various arrangements have heretofore been` proposed for operating one-way. repeaters in two-wire lines, these arrangements involving the idea of switching the repeater at each repeater station under the control of the voice currents so that it will operate to repeat in the direction in which the voice currents are being transmitted. Systems of this type have heretofore been found to be impractical, however, for the reason that the time required for the switching arrangement to respond to the voice current results in suppressing the beginning of-a'syllable.

In accordance with the present invention it is proposed to overcome this diiiiculty by arranging the one-way .repeaters so that they will normally be poled for transmission in one direction.` ln order to reverse the repeaters for transmission 1n the opposite direction a controlling arrangement will be this signaling current actuating switching mechanisms at each repeater point for suitf ably rearranging the circuit of the repeaters to reverse the direction o f transmission. In

transmitted ahead of the voice current adelaynetwork is provlded at the controlling station. The voice current entering the controlling. station at once actuates the operat- *A echo an .singing difficulties are eliminated v about twice as far apart as in a balanced reoperation of the master unit .located at the terminal. This master unit employs only two delay networks and voice operated relays. The switching arrangements at the repeater points are quite simple and. the repeaters themselves are therefore much more simple and inexpensive than if each repeater were in itself a'complete voice operatedunit. The system, by arranging for the reversal of the repeaters before the voice currents arrive at the repeater points, eliminates the possibility of cutting off the initial syllable of a word.

The invention may now be more fully understood from the following description when read in connection with the accompanying drawing, Figure 1 of which shows the general layout of the system with the details of terminal control circuit, Fig. 2 of which shows the details of the repeater unit, Figs. `3 and .4 of which show schematically two different arrangements of the repeaters and F ig. 5'of which illustrates a` modified form of repeater unit.

Referring to Fig. l, a transmission line L is illustrated having a control circuit at station B and reversible'repeaters at stations C, D, E and F, etc. A control circuit is only required-at one terminal for the reason that the reversible repeaters are normally poled to repeat in the direction from the opposittJ terminal to the control terminal and the control for .reversing them need only be exercised when transmitting from the control terminal.

The control circuit "comprises vessentially a 22-type of repeater circuit having amplifiers AE andAW Connected to the line sections through hybrid ooils l() and l1,v the line sections being balanced` by networks N andv N. A delay circuit or-network is associated with veach amplifier, as indicated at 'DE and DW. `Bri-dged across the repeater path east in frontof the delay circuit DE is an echo suppressor unit SE. A similar echo suppressor vunit SW is bridged across the path transmittin west in front of the deunits are of a type well known in the art, the detailed arrangements being illustrated,

"lay circuit Dl/ These echo suppressor (it being unnecessary .to balance the re- ,Y peaters) and the repeaters may be spaced- A for example, in the application of. George the hybrid coil or echoes due to unbalance Crisson, Serial No. 67 0,741, filed October 25, 1923, and include suitable vacuum tube amplifying and rectifying apparatus for rectifying the voice currents to operate. lthe relay.l When voice currents are transmitted from west to east the suppressor SE will actuate its relay in response to the voice currents to short circuit the repeater path transmitting west so ythat the repeater 'is then only capable of transmitting from west to east. When voice currents are transmit# ted from'east to west the suppressorSW actuates its relay to short circuit the repeater path from west to east so that the repeater will now only transmit from east to west.

The delay circuits associated with each repeater path delay the transmission of the voice currents through a given path for a sufficient time to enable the suppressor to short circuit othe opposite path before the voice currents have been transmitted through and back over the other path in the opposite direction. The suppressor SE has its relay provided with an 'extra contact, 12, which normally short circuits a source of oscillations G. Vhen the suppressor SE is actuated in response to voice currents transmitted from west to east, `-the contact 12 is opened and the generator G at oncev trans- `mits oscillations of the frequency of thc generator to the line L through a high *pass filter 13. The frequency transmitted by the generator G acts as the controlling current A to be transmitted over the line for the pur-` pose ofreversing the repeaters at the subsequent .repeater' stations C, D, E and F, as

will be described later. The controlling current is not delayed in its transmission by anydelay circuit, as is' the case with the voice and consequently is transmitted vover. the llne before the voice currentarrives at the hybrid coil. This controlling-current` may be either a hi h or lovin.1 frequencybutf for purposes o f il ustration is herein 'referred to as a high frequency just above the voice currents but'within the'cut-off limits -of the transmission line. Duringtransmis 4sion from West to east the cntrolling frequency will be transmitted over the jline along` with voice currents but will be sepav rated therefrom when necessary byl means of filters, as will be describedl later.

The delay circuit- DE should beso desiiiied that bythe time 'thevoice" wave, w

ch operated the echo suppressor, getsff.

through the delay circuit the controlling wave Will have been transmitted! over the line to reverse all ofthe repeaters at the subsequent stations. As will be' described later, the repeaters, when reversed, remain reversed as long as the control current is transmitted and the control current will be transmitted as long as the talking continues in releasing their contacts.

from west to east When talking from west to east ceases, however, the repeaters return to normal ready for transmission from east to west, the return to normal taking place afterv a slight interval to permit the last syllable'to get throughthe delay circuit and be transmitted. The necessary hangover in-` terval may be provided by designing the echo Suppressors in a manner well known in the art so. that they will be somewhatslow For example, the echo suppressor SE should be designed to have a sufficient hangover time to permit the last voice wave of a train of Waves to pass through the delay circuit DE before the echo suppressor will actually release its contact. i

In transmitting from east to west, no control current will be transmitted as there is no controlling station at the east terminal. The voice currents, however, in passing over the line to the control terminal B are trans' be actuated as soon as the volce currents arf rive at the input side ofthe delay circuit to short circuit the path transmitting east. In transmitting from east to west' the reversible repeaters need notbe .actuated as they are normally poled for transmission in this direction and return to their normal poling as soon a's'transmission from West to east ceases. y

The reversible repeaters to beemployed at repeater points to the east of the control station B may be of the type illustrated in Fig. 2. Asshown in said figurethe control currents transmitted from west to east may be separated from the voicel currents by the high pass filter 15 and transmitted over a circuit `16 to the ampliiier A, interconnectQ ing the'input circuit v17 with the output circuit 18. The lcontrol currents, after passing through the amplifier, aretransmitted to a l detectorD and operate a relay 19, which controls'the switching operation of the ,re-

peater.

This control is exercised throu h two relaysl20 and 21. ,The contacts of t ese'relays are so arranged that normally the input circuit .22 andthe output circuit 23 areshort circlted to prevent transmission from west to east', while the input circuit `17 and the output circuit 18l are operated totransmit :fromeast-to west. When the relays 20 and 2lfa're actuated, however; vinput circuit 17 and output circuit 18 are opened to prevent transmission'from east to west and the short circuits are removed from input circuit 22 and output circuit 23 to permit transmission from west to east. This operation depends merely uponthe break of the contacts of the relays and does not depend upon the armature being completely attracted to its make position. Consequently, the action of the relays is very fast and the delay circuit at the controlling station' need not be excessively long.

A low pass filter 24 Aseparates the voice currents transmitted from west to east from the controlling currentso that the voice cur rents may he transmitted through the transformer 25 to the input circuit 22. After the operation of the reversible relays 20 and 21 the voice currents may then be transmitted fiom the amplifier A tothe output circuit 23 und thence through the transformer 26 anda low pass filter 27 to the next line section. through the. circuit 16 and thro-ugh the amplifier A to actuate the detector D are also transmitted overthe ycircuit 28 and 'through the high pass filter 29 to the line section east. It will be noted that resistances are provided in the input and output circuits.

direction) and pass through transformer 30- into the input circuit 17, this circuit being closed over the lower. back contact of relay 21. The voice currents are prevented from passing into the line section west via circuit 16 by reason of the highv pass filter 15 and cannot pass through the -input circuit 22 to the transformer 25 hy reason of the short circuit over the lowerback contact of relay 20. The ldetector D is so arranged by tuning or otherwise as not to respond to voice currents and the short circuit aero-ss the output circuit 23 prevents the voice currents from being transmitted east through the transformer 26. "The amplied voice currents therefor npass from the output circuit 18 through the transformer 31 and low pass lter 24 to the next adjacent line section west.

At the succeeding repeater stations E, D and C, similar actions taken place and the voice currents finally arrive at -the controll station B, where they are transmitted through the low pass filter 14 and hyhrid coil 11 to the delay circuit DW. The echo suppressor SW, which is bridged across the input side of the delay circuit DW, is actuated by the voice currents and short circuits the repeater pat-h transmitting 'east before A the initial voice ware has passed through the delay circuit DW to the :amplifier AW. The voice' currents, after heing The controlling currents passing' passed through the'delay circuit, are amplified by the amplifier AW and are then trans- "mitted to the West line terminal.

Voice currents incoming from the west terminal of Fig. l are transmitted to the input side of the delay circuit DE and operate the echo suppressor SE to short circuit the repeater path in the opposite direction. At -the saine time the contact 12is opened and the control frequency from the generator G is transmitted through ythe filter 13 to the line L. The control frequency is transmit-ted to the line L before the voice currents have been transmitted through the delay circuit to the amplifier AE. As the control frequency is transmitted over the line and arrives at the repeater station C, it is selected by a high pass 'filter l'intothe circuit 16 and impressed upon the amplier A. The control frequency is amplified by the. amplifierA and transmitted to the detector D. The detector D rectifies the control frequency, thereby actuating the relay 19,

the upper contact removes the short circuit V from output 23. A part of the amplified controlling current is transmitted over the circuit 28 through the high pass filter 29 1 and passes along over the line L to the l switching repeater at the next station.

The voice frequency incoming to the ref peater station just discussed passes through the iow `pass filter 24 throu h .transformer 25 and into .input circuit 22, om which cir-V cuit it is impressed upon the amplifier A..

-After being amplified the voice energy passes through the output circuit 23 and the transformer 26 and thence through the low pass filter 27 to the line to he transmitted to Y the next repeater, which in the meantiine will have heenv reversed by the control cur-V rent. This operation is continued until the last repeater station has been passed and the voice currents are impressed upon the terminal line.

The schematic arrangement of the circuit just described is indicated in Fig. 3, in which the rectangle at BY designates the terminal control arrangement and the rectangles at C, D, E and F represent reversibile repeaters which may he of ,the type shown in Fig. 2. Between the last reversible repeater and the terminal line a low pass lter may he insertl ed, as indicated, this being for the purpose of preventing the-control frequency from being transmitted over the terminal line.

`tihile, as already stated, the cont-rol frerae quency may be either below or above the voice range it is possible to use different control frequencies for different circuits and if desired, all of the control frequencies may be above the voice range. By transmitting the control frequency over a separate control circuit a common control circuit may be used for controlling the repeaters of a number of' lilies. An arrangement of this character is shown in Fig. 4, in which L and L are transmission lines provided with reversible repeaters at the points designated RR, each line having a terminal control arrangeiiicnt at the point corresponding to station B of Fig 3. The control frequency sent out by each control arrangement will be different and will be passed through a suitable band filter to a common control line L. The control frequencies sent out along the line L are selected@ at each repeater station through proper band filters and are impressed upon the controlling apparatus of the reversible repeater arrangement at each station. The reversible repeater apparatus may be as shown in Fig. 2, the circuit 16 in this case being, however, opened by switch 50 and the input of amplifier A connected by circuit 16 through the band filter BF to the control line L instead of to the transmission line over which the voice currents are transmitted. As circuit 28 and filter 29 are not necessary when used in the system of Fig. 4 these elements may be cut out by means of switches 51 and 52.

Fig. 5 shows another arrangement of reversible repeater which may be used instead of the reversible repeater of Fig. 2. In this case therepeater is provided with two amcxplifiers, one amplifier AE being used for transmission from west to east and the other amplifier AW being used for transmission from east to west. These amplifiers are associated with the line terminals through hybrid coils 10- and 11', the line terminals being balanced by suitable network such as VNW and NE. Low pass filters 40 and 41 are included in the amplifier paths to pre-l vent the control frequencies from entering the repeater paths. The control frequency is carried through a high pass filter 42 into La circuit 43, which includes an amplifier A.

The outputcircuit 44 of the amplifier is connected to the east-line terminal.-

A detector amplifier arrangement D- is bridged across the circuit 44 and controls by means of a relay 45 the two repeater paths. Normally, with the relay deenergized, the lower repeater path is closed at the righthand back contact of tlie relay so that transmission may takeplace from east to west, while the upper repeater, path is short. circuited at the lefthand back contact of the relay to prevent transmission from west to east. lVhen the control current arrives, however, and passes into the circuit 43, the

ciples herein disclosed may be embodied ininany other organizations widely different from those illustrated without departing from the spirit ofthe invention as defined in the following claims.

What is claimed is:

1. A repeater system comprising reversible repeaters at points along a transmission line, means associated with each 'repeater to reverse 'the direction of such repeater in response to an alternating control current, a terminal control station, and means at said coiitrolstation responsive to voice currents to transmit an alternating control current to the reversible repeaters.

2. A repeater system comprising reversible repeaters at points along a transmission line, means associated with each repeater to reverse the direction of such repeater in response to a control current. a terminal control station, means at said control station responsive to voice currents to transmit a control current to the reversible repeaters, and means 'to delay the transmission of the voice currents until the control current has been transmited.

3. In aarepeater system, a plurality of reversible repeaters at points along a transmission line, said-repeaters normally transan alternating controlling current to the reversible repeaters.

4. In a repeater system, a plurality of reversible repeaters at points along a transmission line, said repeaters normally transmitting in one direction, means associated with said repeaters to reverse the direction of transmission thereof in response to a control current and to restore the repeaters to their normalcondition when the control current ceases, a terminal control station, means at said station responsive to voice currents for transmitting a controlling current to the re- `versible repeaters, and means to -delay the transmission of the voice frequencies to tlie reversible 'repeaters until after the control current has been transmitted.

'5. A repeater system comprising a plurality of reversible :epeaters at points along a transmission line, said repeaters being arranged to transmit normally in one direction,

switching means associated with said repeaters for rearranging the circuits so as to transmit in the op osite direction, controlling means for sald switchin means responsive to alternating controllln currents,

repeaters for rearranging thev circuits so as to transmit in the opposite direction, controlling means for said switching means responsive to controlling currents, a terminal controlling station, means at4 said controlling station responsive to voice currents for transmitting controlling currents to said reversible repeaters,'and means to dela the transmission of voice currents from sai controlling station until after the controlling currents have been transmitted.

7. A repeater system comprising reversible repeaters at different points alon a transmission line, means associated wit each repeater for reversin the direction thereof in responseto contro g currents, a terminal controlling station comprising a two-way repeater circuit having one path 'for transmission in one direction and the -other path for transmission in the opposite direction, delay.

'circuits in each path, voice operated means associated with each path on the input side of the delay circuit to render the o posite path inoperative and means control ed by said voice operating means to transmit a controlling current to the reversible repeaters.

8. A repeater system comprising reversible repeaters at different points along a transmission line, means associated with each repeater for reversing the direction thereof in response to control ing currents, a terminal lcontrolling station com lrising a two-repeater circuit having one at for transmission in vone direction and t e other path for transmissionin the o osite direction, delay circuits in each patill, voice operated means as-I sociated with each path o n the input side of the delay circuit to render the o posite path inoperative. and means contro ed by said voice operated means to transmit a controlling current to the reversible repeaters, said'last mentioned means being elective to transmit said controlling currents before the voice currents have passed the delay circuit.

In testimony whereof, I have si ed'my name to this specification this 17th day of october 1923.

' HENRY A. BARTON. 

